tissues and cellular environment Flashcards
what must cell infrastructures be to be sucessful
malleable enough to cope with stress, changing environments and allow repairs
describe tissues
cells with similar functions connected
organised then into organs
form is related to function
whats a cytoskeleton
internal structure of a cell to give it strength
without it the cell would be floppy and have no support
what are actin filments
part of cytoskelton
provide mechanical stiffness and allow cell movement and contraction
how do actin filaments grow?
monomers join at the plus end and bound by ATP
what is a microtubule
cytoskeleton
esential for cell division
ued to position organelles, proving transport withi the cell
help with shape an movement
what is a microtubule made of
repeating units of tubulin which come together to make hollow tubes
how does a microtubule grow?
monomers join at the plus end and bound to GTP
have organising centres where the minus end is anchored
what is an intermediate filament
more diverse, made of lots of proteins
provide mechanical strength of the cell
used to connect cells together in tissues
roles of the intermeidate filaments
connect cells
forms for basal lamina
anchors chromosomes to the nucleus
how do actin filaments help cells to move
entire actin network can be remodelled very easily
extend and contract contantly and quickly
push out the plasma membrane as the cell senses its envrironment
role of cytoskeltal filaments during cell division
actin: : cut the cell in the middle for cell division
microtubules: pull the chromosomes apart from the centre
name the process of actin filaments growth
treadmilling
property of microtubule growth
shrink faster than they grow so are dynamically instable
they need to keep adding quckly to stay stable
caps on ends help stability
what is cell migrations key steps
protrusion
adhesion
retracton
when is cell migration key?
spread of cancers
formation of new blood vessles
wound repair
embryo development
how do cells migrate?
reoganise the cytokeleton
whats the role of actin in cell migration
growth of actin at the front pushes membrane forward
peice of actin then ataches to thesurface allowing the cells to push forward
why is treadmilling important
cell has finite pool of actin monmers to use
so needs to constantly reuse them
dissassemble at minus end, reassemble at plus end using ATP
what is chemotaxis
a form of cell migration
cel responds to signals from the envronment such as chemicals
again, uses the actin filaments to propagate the movement
how are mehanical stesses trasmitted?
cell to cell by skeetal filaments anchoredd to cell-matrix and cell-cell adhesion sites
how are stresses of tenion and compressin handled?
dealt with by the ECM and it bears it
examples to corrdianted movement and actions:
muscles for contraction
fusing of skeletal muscle to mkae longer cells working together
types of cell junctions
tight junctions
desmosomes
gap junctions
what joins/connects cels
cadherin molecules
how do cells join
they can regnognise eahc other and those doing the same funcion
recognise the cell with came receptor types and form connection based on these
cadherins are types of molcule to help with this
how does a demosome work
connects cells through intermediate filaments
outside of cells are cadherin molecules
conect to filamentes
not a direct link so an anchor of proteins
what are the role of proteins in the demosomsome
act as an anchor between the cadherin molecule on outside of the cell and intermiate filaments on the inside
act as the direct link between the two
what is a tight junction
secondary connections after desmosomes
close junctions
forms an imperable barrier between the cells
how does a tight junction work?
proteins in eahc cell link to the actin cytoskeleton
this joins the cytoskeleton of the two cells
transmembrane protein such as Claudin can aslo do this and form links and bind
what is a gap jucntion
channel proteins that align between cells forming a small pore
function of a gap juction
links two cells cytoplama and direct communication between the two can occur
- exchange of metabolites
- passage of signals
- adhesion between cells
- strength and tumour supression
how does caner arise?
cells gone wrong
they break connections and lose coherence
can now move freely
how do embyors develop cell in the correct environment
cells move around the body durin the development
specalised cells navigate the environment to find the right place and form the connections they need
what is ECM
what cells attach to
scaffolding
provides structure and both mechanical and biochemical support
provides nutrients for the cells
what is the basememt layer
thin sheets of ECM at the base of tissues such as skin or blood vessles
impermeable barrier
what is the ECM made up of
mix of molecules secreted by the cells themselves:
- long proteins such as collagen
- large sugar coated proteins such as protegylcans
- fibronectin
what is collagen
most abundant protein in the body
structural
what does collagen form
molecular cables strengthening tendons, bonds an teeth
also protects and supports solft tissues and connect them to the skeleton
what is collagen formed of?
complex chains wound together into a tight triple helix
features and uses of collagen for cells
- absorbs shock
- cancer cells drag themselve along it
- cell attached to ECm and thus colagen too
what is fibronectin
large glycoprotein
how does fibronectin work in the ECM
contain domains that bind to other ecm components and also binds to integrins
attach the ecm
functins of fibronectinq
key for wound healing, blood clot formation
connects and organises everything
gives organisation and support
what is proteoglycan
proteins heavy glycosylated
contain long chains of sugar molecules branching off the main protein chain
function sof proteoglycans
lubricate the ecm
modify and stabilise the activity of other proteins in the ecm
help prevent the tissues being stiff and inflexible
how has the naked mole rat overcome cancer?
sugar molecules in the ecm are much larger
provides extra protection
makes tissues extra flexible in small spaces
the sugars trap cells in the ecm and they cant break away, you can damage the cell but the ecm wont let it grow out of control
how do cells attach to the ECM
integrins
how do integrin work?
act as matrix receptors
connect the cell to the ECM and transmit signals into the cell allowing it to sense and respond to the environment
outside in signalling
what is outside in signalling
transmitting signals into the cell form an integrin allowing the cell to sense and respond to the environment
what is inside- out signalling
cells being able to recognise the ECM by pulling on the fibres using integrins
purpose of an integrin
recognise the ECM and bind to it
connecting cells to the ecm
what is an adesion complex?
connection point betwen cells and the ECM
how do cells actually move?
combination of actin polymerisation pyshing the plasma membrane forward and integrin molecules binding ti ecm leading to formation of small adhesion complexes
motor proteins on actin then create forces pulling the cel forward
adhesion complex disassembles ad cycle repeats
name a motor protein used for cell movement
myosin
where are flagella found
sperm and bacteria
what are cillia
unicellular organisms used for movement and removal of particles in the air
eg. mucus in respiratory tract
how do cillia and flagella work
motor proteins attach to microtubules, dyenin
which types of cell need to move through the ECM
immune cells or those in tissue repair
how do cells move through the ecm
cells can secrete degradative enzymes to digest some of the ecm
which cells are used for ecm remodelling
fibroblasts
how can cancer cells move through the ecm?
acquire the ability to degrade the ecm and push through
co-opt fibroblasts to help them make tunnels through the ecm
how do cells attach to the basement membrane?
hemi-desmosomes
what is a hemi-desmosome
connects the ECM to intermediate filaments in the cell
link goes through the integrins
